I tried doing it 2 years ago (well, I was writing fanfic, so I wasn't participating in the actual contest part of it, just using the atmosphere and challenge to get some writing done). While I didn't finish the story I was writing I did manage to get 10K of it written over the weekend, it was pretty awesome.
There's going to be mad writing at the house this year for it, and I'm thinking trying it again myself.
Except, the thing is (and you guys may have noticed this ;) I'm more of a podficcer than I am a writer. So I was thinking of changing it from a 3 day novel writing weekend, so a 3 day novel podficcing weekend! I want to get at least 10K read and edited in a weekend!
Anyone want to join me?